Saturday, December 14, 2013

The Net Energy Neutral Wastewater Treatment Plant

From Stanford University - link. The goal of energy reduction and even neutral energy requirements will be a significant focus for wastewater researchers and practitioners this decade.

"A major goal of wastewater
treatment is net energy neutral or net energy producing treatment processes that
remove oxygen depleting forms of carbon and nitrogen. While the treatment of
waste carbon via processes such as anaerobic digestion or gasification enable
energy recovery, the treatment of waste nitrogen requires energy inputs. My
research at Stanford has focused on the development of a a new wastewater
treatment process that recovers energy from waste nitrogen by converting
reactive nitrogen (i.e. ammonia) to nitrogen gas via a nitrous oxide
intermediate. This process is termed the Coupled Aerobic-anoxic Nitrous
Decomposition Operation (CANDO) and involves 3 steps: (1) oxidation of ammonia
to nitrite, (2) reduction of nitrite to nitrous oxide, (3)
decomposition/combustion of nitrous oxide to nitrogen and oxygen gas with energy
recovery. Step (1) of CANDO has been developed by European researches and is
termed the Single reactor system for High activity Ammonia Removal Over Nitrite
(SHARON) process. My research has focused on the development of a biological
process that enables partial reduction of nitrite to nitrous oxide. My research
has also focused on the development of devices that enable catalytic
decomposition of nitrous oxide with a net energy output.

When coupled with
anaerobic digestion, CANDO has the potential to enable net energy producing
wastewater treatment by recovering significant amounts of energy through the
combustion of biogas (i.e. methane) and nitrous oxide. The impact of energy
recovery from wastewater is significant, considering that the treatment and
transport of wastewater imposes a 3% load on U.S. energy supply and
approximately 3-5% in most countries around the world. In principle, CANDO is
applicable to any high concentration ammonia streams including landfill
leachates and industrial manufacturing processes."

1 comment:

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